brain & cranial nerves
DESCRIPTION
BRAIN & CRANIAL NERVES. The brain and spinal cord develop from ectoderm. The brain and spinal cord develop from the neural tube. Prosencephalon (Forebrain) Mesencephalon ( Midbrain) Rhombencephalon (Hindbrain) Primary brain vesicles are present around the 3rd week of development. - PowerPoint PPT PresentationTRANSCRIPT
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BRAIN & CRANIAL NERVES
The brain and spinal cord develop from ectoderm
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The brain and spinal cord develop from the neural tube
• Prosencephalon (Forebrain)• Mesencephalon ( Midbrain)• Rhombencephalon (Hindbrain)
• Primary brain vesicles are present around the 3rd week of development
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Prosencephalon (forebrain)
• Differentiates in 5th week into:• Telencephalon
–cerebral hemispheres
• Diencephalon–thalamus; hypothalamus–pineal gland
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Midbrain
• Mesencephalon remains the same• Brainstem = midbrain
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Rhombencephalon
• Metencephalon–cerebellum, pons
• Myelencephalon–medulla oblongata
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Meninges
• Dura mater–dural septa (extensions): falx cerebri, falx
cerebelli, tentorium cerebelli
• Arachnoid• Pia mater
• Cavities–subarachnoid space, subdural space
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4 Ventricles filled with CSF
• Lateral ventricles (paired)–Interventricular foramen – connects to 3rd
ventricle• Third ventricle
–Cerebral aqueduct – connects 3rd and 4th ventricles
• Fourth ventricle–Connects with central canal of spinal cord
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Cerebrospinal Fluid
• Clear, colorless fluid that protects brain
• Formed by the choroid plexus• Absorbed by arachnoid villi
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Parts of the Brain
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Medulla oblongata• Major reflex center for the cardiovascular and
respiratory system– vasomotor, vasoconstriction
• Pyramids - decussation (crossing) center for motor `tracts
• Non-vital center for coughing, hiccuping, swallowing, vomiting
• Ascending/descending fibers pass through• Cranial nerves VIII-XII arise here
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PONS• Acts as a bridge connecting the
spinal cord to the brain• Major relay center for voluntary
skeletal movements from the cerebral cortex to the cerebellum
• Coordinates with the medulla to regulate respiration
• Cranial nerves V-VIII emerge here
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Midbrain
• Corpora quadrigemina–Visual and auditory reflex centers
• Cerebral peduncles - containing large fiber tracts going to and from the brain
• Houses the cerebral aqueduct• Cranial Nerves III-IV emerge here
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Thalamus
• Two halves connected by the intermediate mass
• Relay center for ALL sensory cranial and spinal nerves
• Interpretation center for crude awareness of pain, temperature and pressure
• Location of 3rd ventricle
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Hypothalamus• Links the nervous system and
endocrine system• Major regulator of homeostasis• Regulates many ANS functions• Regulates appetite, water balance,
thirst, body temperature• Emotional part of brain - pleasure,
fear, rage
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Cranial Nerves• 12 Pairs
• 1 Olfactory - smell
• 2. Optic - sight
• 3. Oculomotor - eye movements
• 4. Trochlear - eye movements
• 5. Trigeminal - eyes & face, chewing
• 6. Abducens - eyes
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• 7. Facial - facial expression, taste
• 8. Vestibulocochlear - equilibrium, hearing• 9. Glossopharyngeal - tonge & swallowing• 10. Vagus - heart, visceral organs• 11. Accessory - neck & back• 12. Hypoglossal - tongue
Cranial Nerves (continued)
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Cerebellum• Second largest area of the brain• 2 cerebellar hemispheres• Arbor vitae - branchlike pattern• Vermis - wormlike structure that
connects left & right side• Major coordination of skeletal muscle
contraction• Assists with posture and balance
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Cerebrum
• Cerebral cortex - outer layer of gray matter• Two hemispheres separated by longitudinal
fissure• Gyri - ridges on surface• Sulci - grooves on surface• Fissures • Septum pellucidum - thin wall between
ventricles
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Lobes of the Brain
• Frontal• Parietal• Occipital• Temporal• Central sulcus• Lateral sulcus
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Cerebral Dominance
• Left hemisphere–Language–Logic–Math
• Right Hemisphere–Artistic–Musical–Creative
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Cerebral Cortex Specialization• Motor Areas
–Control opposite side of body–Control voluntary motor functions
• Sensory Areas–Detect sensations from opposite side of
body• Association Areas
–Integrate diverse information into purposeful action
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Association Areas
• Prefrontal Cortex – intellect, learning, & personality
• Language Areas–Wernicke’s area – sounding out new words–Brocas’s area – speech
• General Interpretation• Visceral Interpretation
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Basal Ganglia
• Cerebral nuclei• Islands of gray matter located deep within the
white matter• Function: controls large automatic skeletal
muscle movements and produce dopamine
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White Matter
• Commissural fibers (corpus callosum) - connect corresponding parts of two hemispheres
• Association fibers - connect within the same hemisphere
• Projection fibers (higher centers to lower ones)
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Limbic System
• Includes part of thalamus, hypothalamus, and cerebrum
• Emotional brain• Associated with memory• Involuntary behavior for survival• Pleasure and pain centers - fear, sorrow,
affection
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Reticular Formation
• RAS System - reticular activating system• Network of gray matter extending from the
medulla, pons, midbrain into the cortex• Maintains consciousness• Awaken from sleep• Alerts brain of incoming sensory signals